Magnetic resonance imaging (MRI) systems include large magnetic coil structures which create intense magnetic fields in their immediate vicinity. Within an aperture in the coil structure (where a patient is placed), field strengths may be in the range of 2000 Gauss--15,000 Gauss. While the field intensity rapidly decreases with increasing distance from the coil structure, it is known that high residual magnetic fields are still present within the MRI radio frequency (RF) enclosure. For this reason, great care is taken to assure that no magnetic items are allowed to enter the MRI RF enclosure or to be brought into the vicinity of the MRI coil structure.
Certain patient diagnostic procedures are now carried out while the patient is within the MRI unit. During those procedures, it is necessary that the patient's vital signs be monitored. In prior art systems, monitoring equipment had to be located in areas previously determined to have safe magnetic field levels, resulting in limited flexibility in the use of such equipment.
While it is preferred that certain monitoring electronic equipment be maintained within the MRI RF enclosure, there is always a danger that a technician may, in the process of moving the electronic equipment, bring it into a high field intensity area. Such a field can either cause damage to the equipment or distort the patients signals being processed in such a manner as to either mask the patient's vital signs or alter the patient's signals to such an extent that an emergency situation is signalled incorrectly or, potentially more seriously, an emergency signal is masked as a false normal.
Accordingly, there is a need for electronic equipment that can be emplaced within an RF enclosure of an MRI unit and still operate in a manner that assures that accurate patient vital sign signals are produced. Further, there is a need to protect the electronic equipment in the event a technician brings it too close to the MRI unit.